The term laser is an acronym that comes from the English-speaking area, meaning “Light Amplification by Stimulated Emission of Radiation”. The laser is nothing but a light oscillator that allows focusing on a point of a very small diameter, smaller than 1 mm.

The laser cutting alone is the thermal material cutting process, in which the laser source, i.e., the resonator creates a laser beam that is, by means of a mirror, carried out in the cutter head of the machine, focusing on a point of very small diameter.

Laser metal cutting– application and benefits

Due to its high precision, laser cutting has been used in many branches of the industry, some of which are metallurgy, electronics, shipbuilding etc.

Laser metal cutting offers many benefits, and some of them are the following:

• low heat input on metal
• small deformation of the metal
• high speed
• high quality cut
• flexibility
• cost-effectiveness
• precision

The principles of laser metal cutting

Laser metal cutting can be done by:

• CO2 lasers: used when drilling, cutting, marking, engraving
• Nd lasers: most commonly used for drilling. They are characterized by high energy impulses and low speed repetitions
• Nd – YAG lasers: used for drilling, engraving and adjustment. They use very high energy impuls

The illustration of the work of a laser cutting machine

Laser cutting is a thermal process that starts by heating and focusing laser beam (density ranges around 104 Wmm-2) in combination with gas (active or inert). The laser beam melts metal that is being sliced, and gas with its current eliminates the liquefied metal. Laser metal cutting begins by drilling a hole in the metal, and hole drilling can take up to 15 seconds depending on the thickness of the metal. The laser beam applied during the laser cutting process is parallel to a thickness of 1.5 to 12.5 mm.

Laser metal cutting is one of the variations in laser cutting.

An example of a metal cut by a laser is shown below.

Characteristics of laser metal cutting

The precision that can be achieved by laser metal cutting is up to 0.01. The amount of heat that is being introduced during the cutting process, can be seen in the table. The amounts are given in watts [W].

Speed is one of the benefits of laser cutting.

The table below shows the time in minutes needed to cut an inch of material.

Laser metal cutting has several parameters that can be changed, and one of the most important is impulse, that is, continuous beam. Peak power at impulse laser cutting or average power at continuous laser cutting determines penetration. Continuous beam is applied to smooth and thicker material, while impulse beam is used for precise cutting. Comparison of the continuous and the impulse beam cuts can be seen in the photo.

Conclusion

One of the most modern methods of machine metal cutting is laser metal cutting.

The price of laser metal cutting depends on the specific requirements, ie, on the type, the quality and the thickness of the material being cut.

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There are two basic ways of metal cutting:

• Rough processing – is a basic treatment and consists of scraping, drilling, milling, etc. The main object of this kind of processing is to remove a larger quantity of material
• Final processing – broaching, grinding. This procedure is  used to perform the final processing, after the cutting is being done

If metal cutting tools could be divided in groups, they would be divided into:

• Hand metal cutting tools– eg. Hand saws, scissors
• Machine metal cutting tools– laser cutter, plasma cutter, water jet cutting, autogenous cutting, etc.

The decision of how to cut the material depends on the speed, the quality, the precision and general requirements of the cutting. Accordingly, cutting tools are chosen as well.

An example of cutting a material with a hand tool is sheet cutting. When it comes to sheet cutting; scissors (hand or desk) are used in most cases, and there is minimal snout present during the cutting. However, the cutting should be further processed due to the sharp edges that occur in the cutting process.

Machine metal cutting is mostly done by the CNC technology, which has many benefits. Therefore, for example, CNC laser metal cutting, provides a precision of 0.2 mm. Iron cutting is possible as well, by using a CNC and one of the cutters (eg. plasma cutter).

Metal cutting principle

When cutting, the material being cut (sheet metal, iron, steel …) is subject to plastic deformation, the stress of the cut material is increased, it begins to leak, which eventually causes cracking or deformation.  When cutting, snout occurs as well. Moreover, the cut alone in some cutting techniques requires additional processing while in other (eg laser cutting) it doesn’t.

Cutting tools

In addition to the before mentioned division into hand and machine cutting tools, cutting tools can be divided into:

• Tools separating the material by cutting (eg. knife)
• Tools separating the material by particle separation (eg. drill bit)
• Cutting tools without direct contact – energy cutting (eg. plasma cutter)

As has already been mentioned, snout occurs when cutting the material. In some techniques the amount of snout is negligible, while in some it is pretty large.

The amount and the way of forming of the snout depends on the plastic properties of the cut material and can be divided into:

• Broken
• Continuous
• Lamellar

When cutting, forces that affect the heat of the material occur, and the material can be deformed if the amount of heat transferred to it is large. However, today’s sophisticated cutting techniques mostly transmit a minimal amount of heat to the material, so deformation is avoided. In addition, most sophisticated cutting techniques (plasma, laser cutting) leave very little cuts behind, and the cut itself doesn’t need to be further processed.

The development of technology, especially the CNC, increases the precision of cutting. For example, CNC laser metal cutting achieves a precision of 0.2 mm.

Materials used for cutting tool production

When cutting material, apart from the deformation of the material, the depletion of the cutting tool happens as well.

Therefore, the following requirements are posed on the cutting tool:

• Cold cutting tools – up to 200 ° C: depletion, deformation, hitting resistance
• Hot cutting tools – above 200 ° C: depletion, corrosion, hitting resistance

With each cutting tool the following differs:

• Causes that affect wear – heat can increase depletion
• Depletion mechanisms – eg oxidation
• The way it is being used – eg fracture
• Depletion Criteria – Different cutting materials have different criteria when it comes to depletion

Metal cutting is one of the most important processes before any further processing. The development of the CNC technology enabled a high precision of the cut, that is as high as 0.2 mm.

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